Re: RPC protocol problem?
Christopher Klaus (cklaus@shadow.net)
Tue, 23 Aug 94 16:37:23 EDT
>
>
> I just read a post in comp.security.unix entitiled "widespread security hole
> in exporting of filesystems" which claims there are ways to break into a
> system that has filesystems exported to itself.
>
> Does anyone know anything about this? The post said "the trick is to make
> RPC requests via the portmapper, in such a way that they appear to the mount
> daemon to be coming from within the host itself."
>
> The post mentions a program that is "out there" to exploit this hole. If
> anyone has any knowledge of this, could you please post instructions on how
> to test for this.
>
Yes, if you export to yourself and your nfs isnt set up securely, then you
can call the portmapper command to do the mount call. Thus , it appears
the mount command came from localhost. That gets the filehandle to the
intruder and bingo for him. To take corrective measures, dont export to
yourself and/or turn on priviledge port checking within nfs.
Yes, this hole is easily exploited and dont think that most intruders
arent aware of it. I think its a known hole back in 1991.
--
Christopher William Klaus <cklaus@shadow.net> <iss@shadow.net>
Internet Security Systems, Inc. Computer Security Consulting
2209 Summit Place Drive, Penetration Analysis of Networks
Atlanta,GA 30350-2430. (404)998-5871.